Dilated Urinary Tract

History:
Mother is sure of LMP 17th Nov/98 ( EDD = 24/8/99). On ultrasound scan (17/7/99) the average gestational age is only 31 weeks, ie the ultrasound derived EDD=18/9/99.

Findings:
The fetus shows a large bladder, with hydronephrotic kidneys bilaterally. Bladder size:35 x 37 mm. Kidneys: 34x18mm and 36x 18 mm. I think the ureters are also dilatated.

Next Ultrasound:
The patient came for a follow-up scan on 2/8/99. The urinary bladder (2) measures 4 x 4 cms. It failed to empty even after two hours of observation. The kidneys showed pelvicalyceal dilation, and there is also suggestion of ureteric as well as urethral (1) dilation.

An interesting feature was noted on this ultrasound in the form of a 3.5 cm anechoic vessicle (resembling a large yolk sac) near the lower limbs. This was observed to float freely with the umbilical cord loops in the liqor.

Questions that were remaining to answer:
1) What is the vesicle?
2) Is there anything else to look for on a follow-up given otherwise unremarkable anatomy survey?

Follow-up:
Baby boy was delivered by C-Section. He was grossly IUGR with multiple anomalies of the limbs. The baby died two hours after delivery. The umbilical cord showed a pseudocyst.

Thanks to everyone for their suggestions and cooperation.

DR. JOE ANTONY, Cochin, India.

Author's Acknowledgement:
A special thanks to Terry for all the effort you put to discuss this case on OBGYN.net Ultrasound. Thanks also to Martin Necas, Dr. Art Fougner, and others for their comments.